Polymer-supported chelating agent

Inactive Publication Date: 2018-11-29
QATOR FOUND FOR EDUCATION SCI & COMMUNITY DEV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0006]The one-step click reaction avoids the multistep synthesis typically required to make polymer-bound catalysts that are soluble in organic solvents. In model experiments, a range of transition metal salts of Co2+, Ni2+, Cu2+, Pd2+ and Ru3+ were successfully extracted from aqueous or polar organic solutions into immiscible heptane solution of a PIB-bound thioether-thiol sequestrant. This PIB derivative demonstrated an excellent performance with quanti

Problems solved by technology

While catalysis is a key aspect of green chemistry and while homogeneous catalyzed processes using transition metals are now commonly used in synthesis of most drugs and chemical intermediates, the separation of the metal catalysts or their by-products from the desired products remains a problem.
However, they are generally only effective when the solution components and the sequestrant can be intimately mixed.
A crosslinked polys

Method used

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Examples

Experimental program
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Effect test

example 1

Synthesis of the Polymer-Supported Chelating Agent

[0021]Dithiol-functionalized polybutadiene 1 was prepared via a green and simple single step radical thiol-ene “click” reaction between commercially available and inexpensive 1,2-ethanedithiol and alkene-terminated PIB Glissopal 1000 (DPn=18), as depicted in FIG. 1. The desired polymer 1 was obtained as clear viscous liquid in 92% yield and fully characterized by 1H (see FIG. 2) and 13C NMR spectroscopy (see FIG. 3). As is true for other functionalized PIB derivatives, NMR spectroscopy makes it easy to characterize the products, since the signals of the PIB backbone appear in the 1.00-1.50 ppm region, whereas signals of the functional terminus are observed downfield, from 1.50 to 3.00 ppm. In our first attempts, thermal initiation with either 0.1 eq. of di-tert-butyl peroxide (DTBP) or azobisisobutyronitrile (AIBN) at 70° C. led to complete transformation of the PIB alkene in 24 h. However, in both cases, the desired thioether-thiol ...

example 2

Proposed Mechanism of Action

[0023]The PIB-bound sequestrant we prepared contains two different binding sites—thioether and thiol. They have differing complexation activity and affinity to transition metals. 1H NMR spectroscopy titration of 1 with palladium acetate was used to understand better the complexation of 1 to Pd2+ (see FIG. 6). It led to a pronounced change in the chemical shift of the acetate protons from 2.00 ppm to 2.10 ppm that is characteristic for free acetic acid. Saturation was detected at equimolar [Pd2+]:[1] ratio by appearance of the signal of free palladium acetate complex. At this stage, signals of all three methylene groups adjacent to the sulfur atoms in 1 were shifted downfield with significant broadening, whereas the signal of the mercaptan hydrogen at 1.75 ppm disappeared, possibly due to proton exchange. These observations suggest chelation of Pd2+ with both coordination sites (see FIG. 5), similar to chelation with thioglycolic acid.

example 3

Sequestering Transition Metals from Aqueous Solution and Polar Organic Solvent

[0024]A series of experiments were performed to determine the ability of 1 to sequester metals (in particular Cu2+ and Pd2+) from various polar solvents, including water. Our initial studies involved sequestration of transition metal cations such as Co2+, Ni2+, Cu2+, Pd2+ and Ru3+ from solutions of their salts in deionized water, methanol or acetonitrile by a heptane solution of 1. In a typical experiment, a solution of sequestrant in heptane was added to a solution of CuSO4 in water and shaken, with resulting formation of an emulsion. Shaking was continued for 2 h. During this time, visually observed discoloration of the aqueous phase qualitatively indicated a high level of Cu2+ sequestration. Quantitative inductively coupled plasma optical emission spectroscopy (ICP-OES) analysis of the polar phase that indicated 60-fold decrease of copper content (Table 1) confirmed this observation. A control experimen...

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Abstract

The polymer-supported chelating agent is polyisobutylene having a thiol-thioether terminal group. The polymer-supported chelating agent is made by reaction of the terminal carbon double bond of polyisobutylene with 1,2-ethanedithiol in a one-step click reaction, resulting in PIB functionalized with a thiol-thioether sequestering group. In use, the polymer-supported chelating agent is added to a biphasic solvent system containing a transition metal in solution for removal of the transition metal by liquid/liquid extraction. The transition metal is chelated or sequestered by the chelating agent and removed in a nonpolar organic phase, such as heptane.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]This application claims the benefit of U.S. Provisional Patent Application Ser. No. 62 / 511,327, filed May 25, 2017.BACKGROUND1. Field[0002]The disclosure of the present patent application relates to chemical separations, and particularly to a polymer-supported chelating agent for recovering a transition metal catalyst from a reaction mixture.2. Description of the Related Art[0003]While catalysis is a key aspect of green chemistry and while homogeneous catalyzed processes using transition metals are now commonly used in synthesis of most drugs and chemical intermediates, the separation of the metal catalysts or their by-products from the desired products remains a problem. This issue has been addressed in a variety of ways. The established approach to address this problem is to use solid state sequestrants. There is an immense arsenal of ion exchange resins and functionalized inorganic supports that can sequester metals or metal catalyst re...

Claims

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Application Information

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IPC IPC(8): B01J20/26B01J20/30C08F8/34C22B3/00C22B7/00C22B15/00C22B3/16
CPCB01J20/265B01J20/3085C08F8/34C22B11/048C22B7/009C22B15/0065C22B3/1616B01J31/0217B01J31/0218B01J31/403B01J31/4038B01J45/00
Inventor BAZZI, HASSAN SAIDAL-HASHIMI, MOHAMMEDBERGBREITER, DAVID E.CHOUIKHI, DALILA
Owner QATOR FOUND FOR EDUCATION SCI & COMMUNITY DEV
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